The retina is the part of the eye that is sensitive to light. The macula lutea is the region of the retina that allows us to read and recognize faces. Diseases of the macula, such as age-related macular degeneration and diabetic macular edema, account for a major proportion of legal blindness. To combat these diseases, a variety of accepted and experimental medications are employed via systemic routes or local, invasive surgical procedures.
A remarkable increase in knowledge and interest surrounding the pharmacologic treatment of macular and retinal diseases has occurred. As a result, a variety of promising agents are now being investigated for their effects on such blinding disorders as exudative age-related macular degeneration, diabetic retinopathy, macular edema, retinoblastoma, and other diseases of the retina and macula lutea. Currently, these drugs are delivered to the macula and retina via local, invasive surgical procedures, such as intravitreal or periorbital injections, or via systemic routes. Surgical methods often require repeated injections and may lead to serious ocular complications, including endophthalmitis, retinal detachment, and vitreous hemorrhage. Likewise, systemic administration is associated with a variety of potential systemic side effects and with the difficulty of delivering therapeutic levels of the drugs to the retina.
Given the recent advances in developing pharmacologic treatments for a variety of macular and retinal diseases, improving drug targeting and delivery are of paramount importance. For example, retinoblastoma, a neoplastic process that arises from the retina, is the most common primary ocular cancer of childhood. Though once treated almost exclusively with radiation or eye removal (enucleation), systemic chemotherapy is now the sight and lifesaving therapy of choice. In addition, various anti-inflammatory and anti-angiogenic agents are being investigated for use in treating exudative age-related macular degeneration (AMD) (the leading cause of legal blindness in the elderly) and for diabetic retinopathy (the leading cause of blindness in working Americans). In order to advance the noninvasive, pharmacologic treatment of retinoblastoma and other retinal diseases, new drugs having improved delivery to the retina are needed.